Furthermore, they say the tool DHS used to demand the information — a Customs and Border Patrol administrative summons — is only meant to allow CBP to demand information about imported merchandise. “It is apparent that whatever investigation Defendants are conducting here does not pertain to imported merchandise,” the complaint says.

As a side note, they point out that the summons was delivered on March 14, with a deadline of March 13 — that is, already in the past.

The larger question is one of First Amendment rights, the company maintains.

“Compelled disclosure of the identities of Twitter users who have engaged in pseudonymous speech would chill their exercise of the constitutionally protected right to speak anonymously,” Twitter’s lawyers write.

“A time-honored tradition of pseudonymous free speech on matters of public moment runs deep in the political life of America,” they note elsewhere

NPR’s Laura Sydell reports that this isn’t the first time Twitter has gone to court over users’ privacy.

“Twitter has resisted other government attempts for information about its users including a demand from New York prosecutors for information about an Occupy Wall Street protester in 2012,” Laura says. “Twitter lost that case.”

Twitter and DHS both declined to comment about the new litigation.

The user behind @ALT_uscis has responded, however, with several tweets.